1. Field of the Invention
This invention relates generally to apparatus and methods for producing semiconductor chips and, more specifically, to an automatic pellet feeding apparatus and method for delivering plastic pellets to a plastic molding machine for encapsulating semiconductor chips.
2. Description of the Related Art
Automatic molding machines for use in encapsulating semiconductor chips are fed plastic pellets or compressed compound (epoxy) pellets which are heated and subsequently compressed by a plunger. The plunger forces the molten plastic fluid through a conduit and into a cavity having a semiconductor chip therein, thereby encapsulating the semiconductor chip. Typically, the plastic pellets have a generally cylindrical shape, and they are placed with their side in contact with a conveyor belt which delivers the plastic pellets to the automatic molding machine.
In the past, the plastic pellets were delivered from a pellet storage bin to the conveyor belt using a vibration type platform in the following manner. The plastic pellets were forced through a mechanically constrained channel and onto the conveyor belt. The agitation of the plastic pellets caused by the vibrating platform would help to properly align the pellets so that they may move through the constrained channel and onto the conveyor belt in the required in-line position. The vibrating platform approach has several disadvantages. For example, the vibration raises dust and other debris. Additionally, the agitation of the vibration platform sometimes damages the plastic pellets.
Therefore, there existed a need to provide an automatic pellet feeding apparatus that overcomes the shortcomings of the vibration platform type pellet feeding system.